Re: [Qemu-devel] [PATCH 1/2] net: assert that tx packets have nonzero size

[Oleinik, Alexander]

On Tue, 2019-07-23 at 11:38 +0800, Jason Wang wrote:
> On 2019/7/20 上午2:52, Oleinik, Alexander wrote:
> > Virtual devices should not try to send zero-sized packets. The
> > caller
> > should check the size prior to calling qemu_sendv_packet_async.
> > 
> > Signed-off-by: Alexander Oleinik <address@hidden>
> > ---
> >   net/net.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/net/net.c b/net/net.c
> > index 7d4098254f..fad20bc611 100644
> > --- a/net/net.c
> > +++ b/net/net.c
> > @@ -741,6 +741,9 @@ ssize_t qemu_sendv_packet_async(NetClientState
> > *sender,
> >       size_t size = iov_size(iov, iovcnt);
> >       int ret;
> >   
> > +    /* 0-sized packets are unsupported. Check size in the caller
> > */
> > +    assert(size);
> 
> Can this be triggered through a buggy device by guest? If yes, we
> need 
> avoid using assert() here.

Yes - for example, virtio-net could trigger trigger it because there is
no size check prior to qemu_sendv_packet_async, although PATCH 2/2
should fix this.
Instead of the assertion, should we return a negative value?  

> Thanks
> 
> 
> > +
> >       if (size > NET_BUFSIZE) {
> >           return size;
> >       }